This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application entitled Automatic Tilt Adjustment Device and an Optical Recording/Reproducing Apparatus Having the Same earlier filed in the Korean Industrial Property Office on May 3, 1999, and there duly assigned Serial No. 99-15886 by that Office and an application entitled Automatic Tilt Adjustment Device and an Optical Recording/Reproducing Apparatus Having the Same earlier filed in the Korean Industrial Property Office on May 3, 1999, and there duly assigned Serial No. 99-15887 by that Office.
1. Field of the Invention
The present invention relates to an optical recording and reproducing apparatus, and more particularly to an automatic tilt compensator and an optical recording and reproducing apparatus having the same for automatically detecting and compensating for a deformation of a disc which is rotated while the optical recording and reproducing apparatus is operated.
2. Description of the Related Art
An optical recording/reproducing apparatus is a device for recording and/or reproducing desired information on a disc by using an optical device. In such an optical recording/reproducing apparatus, a disc is seated on a turntable by a disc loading apparatus, and rotated at a predetermined speed by a rotating unit, that is, a spindle motor. While the disc is rotated, a pickup unit travels in a radial direction of the disc and radiates a laser beam on the disc, so that the pickup unit reproduces or records information.
At this time, the laser beam radiated from the pickup unit, that is, an optical axis of the laser beam is perpendicular to a surface of the disc, and the pickup unit travels while maintaining a predetermined parallel level with respect to the surface of the disc. If the pickup unit fails to maintain the predetermined level with respect to the surface of the disc, as a result, by certain external factors, that is, a disc tilt or assembly errors of the pickup unit and a feeding part of the pickup unit, a situation occurs in which information can not be reproduced or recorded on a disc. In particular, since a record pit of a Digital Versatile Disc (DVD), which has been in a great demand recently, is smaller than that of a Compact Disc (CD), the Digital Versatile Disc is sensitively responsive to a tilt of a disc.
Accordingly, in a general optical recording/reproducing apparatus, when the pickup unit fails to maintain the predetermined level with respect to a surface of a disc due to the above disc tilt, or assembly errors of the pickup unit and the like, in other words, when a tilt occurs which a laser beam of the pickup unit is not perpendicularly projected with respect to a surface of a disc, a tilt compensator, so called, is provided in the optical recording/reproducing apparatus. The tilt compensator adjusts upwards and downwards a position of the pickup unit to control the level of the pickup unit with respect to a disc.
Such a tilt compensator is structured to adjust the level of the pickup unit with respect to a disc by elevating and lowering a pair of guide shafts according to a tilt degree of the disc in which the pair of guide shafts movably support the pickup unit on a deck base. The tilt compensator of the optical recording/reproducing apparatus as stated above is, however, structured to use an arbitrary standard disc upon assembling the optical recording/reproducing apparatus and to adjust only the level of the pickup unit with respect to the standard disc. That is, during an operation of the optical recording and/or reproducing apparatus, an adjustment of the level of the pickup unit with respect to a seated disc, which is rotated for information recording or reproduction, is impossible. In fact, there is the case that the seated disc is bent upward or downward along the radial direction from its center due to a manufacturing error, etc. Accordingly, as an extreme example, if a disc loaded in the optical recording/reproducing apparatus is tilted in an opposite direction to a disc used for the adjustment of the level of the pickup unit during an assembly of the optical recording/reproducing apparatus, the gap between the disc and the pickup unit is wider or excessively more narrow than the adjusted gap. Therefore, errors upon recording/reproducing information occur, and even worse, the information recording/reproducing may not be achieved. Particularly, the above problem is more serious in the Digital Versatile Disc having a smaller pit than in the compact disc.
An exemplar of the art is Itakura et al. (U.S. Pat. No. 5,978,332, Optical Recording Medium, Tilt Detector, Optical Disk Drive, Tilt Detecting Method, and Tilt Correcting Method, Nov. 2, 1999) discloses using a tracking error signal for detecting the tilt by obtaining the difference in quantities of light received by a photo detector and correcting an error tilt amount detected by the imbalance of the light beam on a mirror surface. Ohmi (U.S. Pat. No. 6,041,030, Optical Disk Recording/Reproducing Device with Eccentric and Incline Chuck Control, Mar. 21, 2000) discloses a chuck to compensate for the tilt angle of an optical disc used for recording. Ichimura et al. (U.S. Pat. No. 6,041,031, Optical Disc Recording/Reproducing Apparatus and Method, Mar. 21, 2000) discloses an optical disc recorder and/or reproducer. Kondo et al. (U.S. Pat. No. 4,502,134, Optical Disc Signal Reproducing System with Tilt Immunization, Feb. 26, 1985) discloses a method of compensating for false tracking correction due to light reflected from the lands as opposed to the pits of a recording medium when the disc is tilted from the optical axis. Namoto et al. (U.S. Pat. No. 5,657,303, Tilt Sensor, Optical Disk, and Tilt Compensating Method for Performing a Stable Tilt Compensating Control, and Apparatus Utilizing the Same, Aug. 12, 1997) discloses a tilt sensor and a tilt compensating mechanism for angularly adjusting the optical pickup to eliminate the tilt. Araki (U.S. Pat. No. 5,909,413, Optical Pickup Apparatus Having Crosstalk Balance and Tilt Correction, Jun. 1, 1999) discloses the generation of a tilt error signal using the information about the inner and outer circumference of a track. Murao (U.S. Pat. No. 5,302,834, Optical Pickup and Tilt Control Device Including a Plurality of Photosensitive Units for Generating Signals Indicating Whether Tilt Correction is Necessary, Apr. 12, 1994) discloses a tilt control device having a parallel flat glass plate for refracting the reflected light beam from the optical system. Ohsato (U.S. Pat. No. 5,153,348, Optical Disk Pickup Device with Tilt Compensation by Electrostriction, May 7, 1996) discloses tilt compensation by electrostriction that makes a mechanical deformation cause by the application of an electric field. Marino (U.S. Pat. No. 5,910,936, Measuring and Compensating for Warp in an Optical Recording Disk, Jun. 8, 1999) discloses compensating for disk warp by calculating the desired tilts of a magnetically suspended actuator while the disk is being read. Kobayashi (U.S. Pat. No. 5,646,916, Track-Lead-In Control Device for Optical Head, Jul. 8, 1997) shows an optical head that can be used for an optical disc and Seidel (U.S. Pat. No. 5,815,480, Method for Calculating and Recording a Start Program Radius Upon a Compact Disc, Sep. 29, 1998) shows a technique for determining the start point for a compact disc recording.
The present invention is disclosed to solve the aforementioned problems, and accordingly it is an object of the present invention to provide an automatic tilt compensator of an optical recording and/or reproducing apparatus for sensing and automatically compensating for a deformation direction and a deformation degree of a disc which is rotated during an operation of the optical recording and/or reproducing apparatus.
It is another object of the present invention to provide an optical recording and/or reproducing apparatus having the automatic tilt compensator for remarkably reducing errors of information recording and/or reproducing.
It is a further object to provide an optical recording and/or reproducing apparatus for a digital versatile disc that can automatically compensate for the tilting of the device.
It is yet another object to provide a device that can provide an automatic tilt compensator that can provide for both a compact disc as well as a digital versatile disc.
It is another object to provide a device that may in a stable and a reliable manner compensate for a tilt of a recording medium in an optical recording and/or reproducing device.
The automatic tilt compensator of the optical recording and/or reproducing apparatus according to the present invention for achieving the above objects, includes a device for detecting a deformation direction and a deformation degree of a disc which is seated and rotated on a disc rotation unit of a deck base of the optical recording/reproducing apparatus, and for generating a signal; and a device for adjusting a level of a pickup unit by elevating and lowering a pair of guide shafts by which the pickup unit is movably supported on the deck base according to the signal from the deformation detecting device.
The deformation detecting device includes a sensor mounted in the pickup unit to detect a height difference between an inner and an outer circumferences of the disc, while being moved in a radial direction of the disc together with the pickup unit; and a control section for determining the deformation direction and the deformation degree of the disc by converting the height difference between the inner and the outer circumferences of the disc by the sensor into an angle, and for outputting the signal to the level adjustment device.
According to a preferred embodiment of the present invention, the level adjustment device includes a motor mounted on the deck base and driven by the signal from the deformation detecting device, to generate a driving force; a cam gear mounted on the deck base to be rotated by the motor, the cam gear having a spiral cam groove; a power transmission to reduce a rotating speed of the motor and transmit the driving force of the motor to the cam gear; and a tilt lever, mounted to be rotated in a normal (or forward) and reverse directions on a pair of hinge blocks fixed to the deck base, to elevate and lower the pair of guide shafts while being normally and reversely rotated about the hinge blocks due to the rotation of the cam gear. The tilt lever includes an actuating protrusion formed on a side thereof to be inserted into the spiral cam groove, and shaft supports provided at another side thereof and having grooves. The guide shafts being inserted into the grooves.
At this point, plate springs are mounted on the shaft supports, to prevent the guide shafts supported by the shaft supports from moving and being separated from the shaft supports during the operation of the tilt lever.
Further, set screws are provided at lower portions of the shaft supports to be in contact with the guide shafts, for manually adjusting the level of the pickup unit by elevating and lowering the guide shafts supported by the shaft supports.
According to another embodiment of the present invention, the level adjustment device includes a motor, driven by the signal from the deformation detecting device, to generate a driving force; a cam gear having a slanted face, and being rotated by the motor; a power transmission to reduce a rotation speed of the motor and transmit the driving force to the cam gear; a tilt lever, mounted to be rotated in a normal and reverse direction within a predetermined angle on the deck base by hinges, for supporting the motor, the cam gear, and the power transmission, the tilt lever having a pair of shaft supports on which grooves are formed to receive ends of the guide shafts; a protrusion fixed to the deck base, having an end being in contact with the slanted face of the cam gear; and a spring, disposed between a fixing end formed on an opposite side of the protrusion of the tilt lever and the deck base, for elastically supporting the tilt lever in one direction with respect to the hinges.
At this point, plate springs are mounted on the shaft supports, to prevent the guide shafts supported by the shaft supports from moving and being separated from the shaft supports.
Further, set screws are provided at lower portions of the shaft supports to be in contact with the guide shafts, for manually adjusting the level of the pickup unit by elevating and lowering the guide shafts supported by the shaft supports.
According to this, if a deformed disc is inserted in the optical recording/reproducing apparatus, since the level of the pickup unit is automatically adjusted according to the deformation direction and the deformation degree of the disc to record and/or reproduce information, errors in recording and/or reproducing the information according to the disc tilt can be reduced.
Further, according to another embodiment of the present invention, since the tilt compensator is constructed as a single constituent, the optical recording/reproducing apparatus can be easily assembled. The optical recording/reproducing apparatus includes a deck base; a disc rotating unit mounted on the deck base for rotating a disc loaded by a disc loading device at a predetermined speed; a pickup unit to reproduce an optical signal and to record information while being traveled in a radial direction of the disc rotated by the disc rotating unit by projecting a laser beam on the disc; a pickup unit feeding device having a pair of guide shafts to movably support the pickup unit over the deck base; a device for detecting a deformation direction and a deformation degree of the disc which is seated and rotated on the disc rotating unit, and for generating a signal; and a device for adjusting a level of a pickup unit by elevating and lowering the pair of guide shafts by which the pickup unit is movably supported by the signal from the deformation detecting means.